1. Field of the Invention
The present invention relates to a multi-layer array type LED (light-emitting diode) device, and particularly relates to a multi-layer array type LED device with high luminous efficiency, which is capable of completely preventing moisture from permeating into the optical elements disposed therein.
2. The Prior Arts
The light-emitting theory of LED takes advantage of the intrinsic properties of semiconductors, which is different from the theory of electric discharging, heat and light-emitting of an incandescent light tube. Because light is emitted when electric current forward flows across the PN junction of a semiconductor, the LED is also called cold light. The LED has the features of high durability, long service life, light weight, low power consumption, and being free of toxic substances like mercury, and thereby it can be widely used in the industry of luminance equipment, and the LEDs are often arranged in an array and often used in electric bulletin boards or traffic signs.
In a conventional method for packaging a multi-layer array type LED, a substrate is provided, and two lead frames are positioned in the lead frame groove of the substrate, and then a package module is injection molded so as to encapsulate and fix the substrate and the two lead frames, and then the LED dices are arranged in the light-emitting area of the substrate, and the LED dices are electrically connected to the two lead frames, and then an insulating protection layer, and a fluorescent layer are sequentially formed on the LED dices, and then the package cover is injected to cover the package module. The LED dices are arranged in an array, and stacked one on top of another so as to form a multi-layered structure.
However, the conventional LED device cannot be used in high-moisture environments, and severe environments such as deep sea, air space, or military. This is because each layer of the packaging structure is not airtightly connected to each other, and therefore the whole packaging structure can not be airtight. Consequently, the moisture can easily enter the interior of the packaging structure, which causes the optical elements in the packaging structure to deteriorate over time. As a result, the conventional packaging structure can not be used in a moist environment because the structural strength thereof will be gradually weakened. On the other hand, the light reflector must be manufactured before it is arranged in the LED device, which would cause the packaging efficiency to go down. In view of the above-mentioned disadvantages, a LED packaging structure, which is capable of completely preventing moisture from permeating through to it, being durable in use, and keeping the performance of optical elements for a long term, shall be provided.